This invention relates generally to the cleaning of tree seedlings after they have been extracted from the ground subsequent to nursery growth. More particularly it relates to an apparatus for vibrating and simultaneously conveying seedlings of the relatively large type in order to remove a substantial amount of accompanying soil from the root structure.
As timber is being commercially harvested from various lands, it is common practice to replant within a reasonable period of time with young seedlings. For example, in the Douglas fir growing region of the United States generally located in the Pacific Northwest, as a section of land is harvested it will then be prepared for replanting usually within a one year period with Douglas fir seedlings, preferrably of a superior genetic stock. This practice, of course, insures the sustained yield of Douglas fir timber and the resulting usable wood fiber. Similar harvesting and replanting techniques are utilized in other sections of the country as well as overseas.
While forest lands may be regenerated by using seed stock, it is the common practice and the practice with the highest economic benefits, to utilize one to two year old seedlings for replanting. In this sense a seedling is a young tree that has an existing root structure and growing stem with branches. These young seedlings are usually grown in nursery environments where they can be cultivated in a controlled environment, assuring not only a high survival rate but also a high quality.
Many of the commercial timber growing companies utilize this process for regenerating their forest lands and, as one would expect, it then becomes desirable to develop a more efficient seedling growing, collection, cleaning, and in general, processing capability to enhance the overhall regeneration effort. In most of the existing processes for growing young seedlings, when they are ready to be collected, a machine capable of lifting the seedlings from their seed beds is employed. An example of such a harvesting apparatus may be seen by referring to U.S. Pat. No. 3,693,721 wherein a mechanized harvesting apparatus is disclosed. Usually the next step in the overall process is to clean the lifted seedlings by attempting to remove the attached soil remaining after the lifting process.
One of the basic problems with this part of the process is that the soil must be removed with minimum harm to the delicate root structure and small stem and branches. Gentle handling is a primary criteria in the entire seedling collection and processing function, and in past practice an undue amount of damage was usually incurred in merely handling the seedlings from lifting to packing. Even with careful manual cleaning of the root system a large amount of damage occurred. Of course the other adverse feature of manual handling is its cost and low rate of productivity.
It therefore becomes necessary to seriously consider the cleaning step in the seedling collection and preparation process in order to make it more efficient. Of course there are several obvious design and performance criteria that arise from the above discussion, among them being minimum damage to the young seedlings, productivity of the cleaning system, efficiency of the soil removal, and overall cost of the system.
Accordingly from the foregoing, one object of the present invention is to provide a seedling cleaning system that is essentially mechanized.
Another object of the present invention is to provide a seedling cleaning system that effectively removes attached soil from the root structures with minimum damage thereto.
Yet a further object is to provide a seedling cleaning system that is of simple construction and low cost.
Yet another object of the present invention is to provide a seedling cleaning system that offers a high rate of seedlings cleaned per unit of time.
These and other objects of the invention will become apparent upon reading the following specification in conjunction with the attached drawing.